The present invention relates to a gear synchronizer assembly for power transmissions, and more particularly to a gear synchronizer mechanism of the type which comprises a gear member rotatably mounted on a transmission shaft, a spline piece mounted on a hub portion of the gear member for rotation therewith and being formed at one side thereof with a conical portion and thereon with external spline teeth, a synchronizer ring mounted on the conical portion of the spline piece for frictional engagement therewith, a hub member fixed to the transmission shaft for rotation therewith and being formed thereon with external spline teeth, a clutch sleeve encircling the hub member and having internal spline teeth in continual engagement with the external spline teeth of the hub member, the clutch sleeve being axially shiftable to be engaged at the internal spline teeth thereof with the external spline teeth of the spline piece, and thrust means for thrusting the synchronizer ring toward the spline piece in shifting operation of the clutch sleeve to effect the frictional engagement between the synchronizer ring and the spline piece.
In such a conventional gear synchronizer means as described above, the thrust mechanism comprises a plurality of circumferentially spaced strut keys each having a raised portion in engagement with the corresponding recess in the inner peripheral wall of the clutch sleeve, and an annular retainer spring arranged to bias the strut keys radially outwardly for engagement with the clutch sleeve. To simplify the thrust means in construction, an improved thrust means has been proposed in Japanese Early Patent Publications Nos. 55-100428, 58-137627, 58-163829, and 58-174724, wherein the strut keys and retainer spring are replaced with a single thrust element. It is, however, difficult to enhance productivity of the gear synchronizer mechanism because the single thrust element is complicated in configuration and construction.
To overcome the shortcomings of such a conventional thrust means as described above, an improved gear synchronizer mechanism has been proposed by the inventors in a copending U.S. patent application No. 677,748, filed on Dec. 3, 1984, now U.S. Pat. No. 4,625,844, wherein the clutch sleeve is formed at its inner periphery with at least one internal radial projection, and wherein the thrust means comprises a radially contractible annular resilient member supported in place by engagement with the inner circumference of a cylindrical hub portion of the hub member, the annular resilient member having an axial leg extending therefrom toward the internal radial projection of the clutch sleeve and having a radial projection arranged to be brought into engagement with the internal radial projection of the clutch sleeve and arranged to abut against and urge the synchronizer ring toward the spline piece upon engagement with the internal radial projection of the clutch sleeve, the axial leg of the annular resilient member being arranged to be compressed radially inwardly by engagement with the internal radial projection of the clutch sleeve.
In the above-described synchronizer mechanism, the synchronizer ring is integrally formed thereon with a pair of raised portions which are formed with a chamfer at each end thereof, and the internal radial projection of the clutch sleeve is formed at one side thereof with a pair of chamfers to be engaged with the chamfers of the raised portions on the synchronizer ring and arranged to pass through an axial groove between the raised portions of the synchronizer ring. In operation, the internal radial projection of the clutch sleeve is engaged at its chamfers with the chamfers of the synchronizer ring to establish a frictional driving connection between the parts to be brought into synchronization. For this reason, if the number of internal radial projections is reduced, there will occur a problem in durability of the radial projections due to increase of the pressure acting thereon. If the number of internal radial projections is increased, there will occur undesired disengagement between the intermeshed spline teeth in deceleration due to reduction of the number of internal spline teeth of the clutch sleeve to be meshed with the teeth of the gear member.